Surface characterization of indirect restorative materials submitted to different etching protocols.

OBJECTIVES: This in vitro study aimed to evaluate the effect of different times and concentrations of hydrofluoric acid etching on the surface of indirect restorative materials obtained from blocks used in CAD-CAM technology. METHODS: Specimens (4 mm × 4 mm × 0.8 mm) were obtained for each indirect restorative material: zirconia-reinforced lithium monosilicate ceramic (Celtra Duo), nanoceramic resin (Lava Ultimate), and polymer-infiltrated ceramic network material (Vita Enamic). The materials were submitted to etching with 5% or 10% hydrofluoric acid for 20, 40, 60, or 90 s. A control group for each material was evaluated without any surface treatment, totaling nine experimental groups for each material (n = 10). The specimens were evaluated for surface roughness (Ra and Rz), confocal optical microscopy, the contact angle (θ), surface free energy (γs), total free interaction energy (∆G) using a goniometer, and microshear bond strength to resin cement. Specimen images were obtained using scanning electron microscopy, confocal optical microscopy, and atomic force microscopy. Data on the surface roughness, the contact angle, surface free energy, total free interaction energy, and bond strength were subjected to two-way ANOVA and Tukey´s test (α=0.05). RESULTS: In general, Celtra Duo showed better results after etching with 10% hydrofluoric acid for 40 or 60 s. Lava Ultimate showed better performance after etching with 10% hydrofluoric acid for 20 or 40 s, whereas Vita Enamic showed better results after etching with 5% hydrofluoric acid for 90 s. CONCLUSION: Each material showed different characteristics after etching with hydrofluoric acid. Knowledge of the proper protocol for each material is essential to ensure improvements in the adhesion process and durability of indirect restorations. In general, Celtra Duo presented mechanical properties superior to those of Lava Ultimate and Vita Enamic. CLINICAL SIGNIFICANCE: Specific etching protocols must be recommended for each indirect material because longer exposure to hydrofluoric acid can jeopardize the surface, thus affecting the mechanical and bond strength properties.

Evaluation of material waste, dimensional stability, and detail reproduction of polyvinyl siloxane impression materials mixed with different mixing tips.

STATEMENT OF PROBLEM: Redesigned mixing tips, promising less impression material waste, have been marketed. However, whether their use adversely affects the dimensional stability and detail reproduction of the impression material is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the dimensional stability, detail reproduction, and material waste of different polyvinyl siloxane impression materials (regular and light-body) mixed with 2 different mixing tips (MIXPAC T-Mixer mixing tip and MIXPAC helical mixing tip). MATERIAL AND METHODS: Six different polyvinyl siloxane impression materials were used in 2 different consistencies: Virtual Monophase and Virtual Light Body (Ivoclar Vivadent AG), Express XT Regular and Express XT Light Body (3M ESPE), and Panasil initial contact Regular and Panasil initial contact Light (Kettenbach). The polyvinyl siloxane impression materials were mixed with 2 different mixing tips: conventional helical and T-Mixer (n=10). The specimens were prepared in a metal matrix as per specification #19 of the American National Standards Institute/American Dental Association (ANSI/ADA) and International Organization for Standardization (ISO) 4823:2015. The materials were mixed with both mixing tips as per the manufacturer's instructions, inserted into a perforated custom tray on the matrix, and allowed to polymerize completely. The dimensional stability was calculated based on the measurement of the reproduction of lines engraved in the metal matrix. Detail reproduction was evaluated through analysis of continuity and reproducibility of those lines, immediately, 7 days, and 14 days after polymerization. Material waste was assessed by the difference between the initial (before mixing) and final weight (after complete polymerization) of both mixing tips. The data on dimensional stability and detail reproduction among the materials were submitted to the Kruskal-Wallis test, followed by the Student-Newman-Keuls test (α=.05). Comparison between the mixing tips was carried out with the Mann-Whitney test (α=.05), while the comparison among the periods of analysis (immediate, 7 days, and 14 days) was carried out with the Friedman test (α=.05). The data on material waste between the mixing tips were submitted to 1-way ANOVA, followed by the Tukey honestly significant difference tests (α=.05). RESULTS: The T-Mixer mixing tip resulted in reduced material waste. For dimensional stability, Virtual Light mixed with T-Mixer resulted in lower dimensional change (0.53 ±0.58%) compared with the helical mixing tip (1.09 ±0.43%). Among the materials, Panasil Light presented higher values of dimensional change at immediate and 7-day analysis when mixed with T-Mixer tip with a statistical difference compared with Express Light, Virtual Light, and Panasil Regular (P<.05). In general, both mixing tips provided similar results in all periods of analysis (P>.05) for qualitative analysis of detail reproduction. CONCLUSIONS: The T-Mixer tip resulted in less material waste compared with the helical mixing tip. In general, light-body materials showed higher dimensional stability when the T-Mixer tip was used compared with the conventional tip. In general, reduced detail reproduction was observed after periods longer than 7 days after impression making.

In vitro study on how cold plasma affects dentin surface characteristics.

PURPOSE: Studies evaluating different features of cold plasma action on dentin surface characteristics are lacking. Thus, this in vitro study aimed to determine the effect of cold plasma under different protocols of exposure time, distance to plasma source, and the association of argon gas with distinct concentrations of oxygen on the wettability, surface energy, total free interaction energy, surface roughness, morphology and chemical composition of dentin. MATERIAL AND METHODS: One hundred and twenty-five bovine dentin samples were used and divided into twenty-five groups according to the exposure time to plasma (15, 30, or 60 s); distance between plasma source and dentin surface (3 or 6 mm); argon gas without plasma generation; and plasma generated by argon gas and association of argon gas with distinct concentrations of oxygen (2 % or 3 %) (n = 5). Contact angle (θ), surface energy (γs) and total free interaction energy (ΔG) were measured using a goniometer (Krüss), while surface roughness (Ra) was evaluated by a profilometer (Mitutoyo). Representative samples were submitted to scanning electron microscopy (JEOL) to ilustrate the morphology and chemical composition of dentin. Data comparing control group with all experimental groups were submitted to ANOVA followed by Tukey's test (α = .05). Data comparing oxygen gas action at different concentrations and argon gas on dentin characteristics were submitted to non-parametric Kruskal-Wallis test, followed by Dunn test for comparison between the groups and methods (α = 0.05). RESULTS: In general, argon gas without plasma generation promoted no significant difference on dentin surface characteristics compared to control group (P > .05), differently for the cold plasma that significantly reduced contact angle values and increased total free interaction energy of dentin surface (P < .05). Overall, feeding of oxygen at distinct concentrations promoted significant difference on dentin surface characteristics compared to control group (P < .05). Exposure time and distance protocols interfered with contact angle, surface energy and total free interaction energy analyses for each gas. There was no significant difference on surface roughness (P > .05), morphology and chemical composition of dentin submitted to argon gas, cold plasma, and distinct concentrations of oxygen. CONCLUSION: In conclusion, plasma generated by argon gas and its feeding with 2 % and 3 % oxygen gas improved the dentin surface characteristics about wettability, surface energy and total free interaction energy. Such treatments preserved the surface roughness, morphology and chemical composition of dentin. The protocols of groups Ar-6mm-15sec, ArO2-3mm-30sec and ArO3-3mm-15sec are recommended for improvement of dentin surface characteristics.

Restaurações cerâmicas multicamadas e monolíticas: uma revisão de literatura / Multilayered and monolithic ceramic restorations: a literature review

Objetivo: realizar uma revisão de literatura sobre materiais, técnicas de confecção, vantagens, desvantagens e limitações das restaurações cerâmicas multicamadas e monolíticas. Revisão de literatura: embora as cerâmicas odontológicas sejam utilizadas para confecção de restaurações dentárias indiretas, porque têm excelentes propriedades mecânicas e estéticas, são materiais susceptíveis à fratura sob forças oclusais. Para compensar essa fragilidade, restaurações multicamadas são confeccionadas associando um material mais resistente para a infraestrutura e a posterior aplicação de cerâmica para recobrimento estético. Porém, as restaurações multicamadas apresentam como desvantagem o possível lascamento da cerâmica de recobrimento. Essas falhas comprometem a restauração funcional e a estética, exigindo a substituição da peça protética em muitos casos. Sendo assim, devido à evolução de sistemas cerâmicos e técnicas de processamento, surgiram as restaurações cerâmicas monolíticas fabricadas com um único material, a fim de superar tal limitação. Nesse sentido, diferentes materiais e técnicas são apresentados na literatura para a confecção de restaurações cerâmicas monolíticas. Considerações finais: as restaurações multicamadas têm bom resultado estético, porém podem apresentar lascamento da cerâmica de recobrimento. Essa limitação é superada pelo uso de um único material para as restaurações monolíticas, mas o resultado estético pode ser limitado. De um modo geral, a literatura demonstra um bom comportamento clínico para as restaurações cerâmicas multicamadas e monolíticas, quando a técnica de confecção e o sistema cerâmico são bem indicados. (AU)

Objective: the aim of this study was to conduct a literature review about the materials, techniques, advantages, disadvantages and limitations of multilayer and monolitic ceramic restorations. Literature review: although dental ceramics have been used for fabrication of dental restorations due to its good esthetic and mechanical properties, it is a material prone to fracture under oclusal loading. To surpass such fragility, multilayer restorations are fabricated using a resistant framework material associated to esthetic veneering ceramic. However, multilayer restorations present risk to chipping of veneering ceramic. Those failures represent a functional and esthetic problem, leading to restoration replacement. So, the evolution of ceramic systems and techniques generated monolitic restorations using a single material. Several materials and techniques are presented in the literature for fabrication of monolitic ceramic restorations. Final considerations: multilayer restorations present good esthetic result but delamination of veneering ceramic can occur. Such limitation is solved using a single material in monolitic restorations, but esthetic result is limited. In general, literature shows appropriate clinical performance for both multilayer and monolitic ceramic restorations when technique and materials are well indicated. (AU)

Efficacy of Sealing Agents on Preload Maintenance of Screw-Retained Implant-Supported Prostheses.

PURPOSE: The aim of this study was to evaluate the effect of sealing agents on preload maintenance of screw joints. MATERIALS AND METHODS: A total of four groups (n = 10 in each group) of abutment/implant systems, including external hexagon implants and antirotational UCLA abutments with a metallic collar in cobalt-chromium alloy, were assessed. In the control group (CG), no sealing agent was used at the abutment screw/implant interface. In the other groups, three different sealing agents were used at the abutment screw/implant interface: anaerobic sealing agent for medium torque (ASMT), anaerobic sealing agent for high torque (ASHT), and cyanoacrylate-based bonding agent (CYAB). All abutments were attached to the implants at 32 ± 1 N.cm. After 48 ± 2 hours of initial tightening, loosing torque (detorque) was measured using a digital torque wrench. Data were analyzed using Shapiro-Wilk, Wilcoxon, and Kruskal-Wallis tests, at 5% level of significance. RESULTS: In the CG and ASMT groups, detorque was lower than the insertion torque (24.6 ± 1.5 N.cm and 24.3 ± 1.1 N.cm, respectively). In the ASHT and CYAB groups, mean detorque increased in comparison to the insertion torque (51.0 ± 7.4 N.cm and 47.7 ± 15.1 N.cm, respectively). CONCLUSION: The ASHT was more efficient than the other sealing agents, increasing the remaining preload (detorque value) 58.88%. Although the cyanoacrylate-based bonding agent also generated high detorque values, the high standard deviation suggested its lower reliability.

Planejamento virtual em cirurgia guiada ­ uma realidade na Implantodontia / Virtual planning in guided surgery ­ a reality in Implantology

O planejamento virtual para cirurgia guiada é uma técnica que vem sendo cada vez mais utilizada na Implantodontia. Sendo assim, o objetivo desse estudo foi realizar uma revisão da literatura sobre a técnica de planejamento virtual para cirurgia guiada sem retalho em reabilitação oral com implantes osseointegráveis, de modo a fornecer informação sobre as características, vantagens e limitações dessa modalidade. Diversos estudos demonstraram a confiabilidade e vantagens da técnica quanto à precisão do planejamento, inserção dos implantes, fabricação da prótese e satisfação do paciente. No entanto, alguns autores relataram que desvios podem ocorrer quanto ao posicionamento dos implantes em relação ao planejamento virtual, o que ressalta a importância da utilização do guia cirúrgico, bem como precisão durante a execução de todas as etapas clínicas e laboratoriais. Concluiu-se que, apesar das limitações relatadas por alguns autores, o método apresenta diversas vantagens que garantem a sua previsibilidade quando indicado e executado corretamente (AU).

The virtual planning for guided surgery has been a widely used technique in Implantology. Thus, the aim of this study was to conduct a literatura review about the virtual planning for flapless guided surgery in oral rehabilitation with dental implants regarding its characteristics, advantages, and limitations. Several studies demonstrated the reliability and advantages of this approach as a consequence of accuracy during treatment planning, implants insertion, prosthesis fabrication, and patient's satisfaction. However, some authors reported deviations of implants positioning compared to the virtual planning, which highlighted the importance of using the surgical guide as well as the accuracy during all clinical and laboratorial steps. Despite of the limitations demonstrated by some authors, it was concluded that this method presents several advantages to enhance its predictability when the procedures are well indicated and performed (AU).

Effect of Atmospheric-Pressure Cold Plasma on Pathogenic Oral Biofilms and In Vitro Reconstituted Oral Epithelium.

Considering the ability of atmospheric-pressure cold plasma (ACP) to disrupt the biofilm matrix and rupture cell structure, it can be an efficient tool against virulent oral biofilms. However, it is fundamental that ACP does not cause damage to oral tissue. So, this study evaluated (1) the antimicrobial effect of ACP on single- and dual-species biofilms of Candida albicans and Staphylococcus aureus as well as (2) the biological safety of ACP on in vitro reconstituted oral epithelium. Standardized cell suspensions of each microorganism were prepared for biofilm culture on acrylic resin discs at 37°C for 48 hours. The biofilms were submitted to ACP treatment at 10 mm of plasma tip-to-sample distance during 60 seconds. Positive controls were penicillin G and fluconazole for S. aureus and C. albicans, respectively. The biofilms were analyzed through counting of viable colonies, confocal laser scanning microscopy, scanning electron microscopy and fluorescence microscopy for detection of reactive oxygen species. The in vitro reconstituted oral epithelium was submitted to similar ACP treatment and analyzed through histology, cytotoxocity test (LDH release), viability test (MTT assay) and imunnohistochemistry (Ki67 expression). All plasma-treated biofilms presented significant log10 CFU/mL reduction, alteration in microorganism/biofilm morphology, and reduced viability in comparison to negative and positive controls. In addition, fluorescence microscopy revealed presence of reactive oxygen species in all plasma-treated biofilms. Low cytotoxicity and high viability were observed in oral epithelium of negative control and plasma group. Histology showed neither sign of necrosis nor significant alteration in plasma-treated epithelium. Ki67-positive cells revealed maintenance of cell proliferation in plasma-treated epithelium. Atmospheric-pressure cold plasma is a promissing approach to eliminate single- and dual-species biofilms of C. albicans and S. aureus without having toxic effects in oral epithelium.

Failure modes of Y-TZP abutments with external hex implant-abutment connection determined by fractographic analysis.

Yttria-stabilized tetragonal zirconia (Y-TZP) was introduced as ceramic implant abutments due to its excellent mechanical properties. However, the damage patterns for Y-TZP abutments are limited in the literature. Fractographic analyses can provide insights as to the failure origin and related mechanisms. The purpose of this study was to analyze fractured Y-TZP abutments to establish fractographic patterns and then possible reasons for failure. Thirty two prefabricated Y-TZP abutments on external hex implants were retrieved from a single-load-to failure test according to the ISO 14801. Fractographic analyses were conducted under polarized-light estereo and scanning electro microscopy. The predominant fracture pattern was abutment fracture at the connecting region. Classic fractographic features such as arrest lines, hackle, and twist hackle established that failure started where Y-TZP abutments were in contact with the retention screw edges. The abutment screw design and the loading point were the reasons for localized stress concentration and fracture patterns.

The influence of bone quality on the biomechanical behavior of full-arch implant-supported fixed prostheses.

We evaluated the influence of bone tissue type on stress distribution in full-arch implant-supported fixed prostheses using a three-dimensional finite element analysis. Stresses in cortical and trabecular bones were also investigated. Edentulous mandible models with four implants inserted into the interforaminal region were constructed from different bone types: type 1 - compact bone; type 2 - compact bone surrounding dense trabecular bone; type 3 - a thin layer of compact bone surrounding trabecular bone; and type 4 - low-quality trabecular bone. The mandible was restored with a full-arch implant-supported fixed prosthesis. A 100-N oblique load was applied to the left lower first molar of the prosthesis. The maximum (σmax) and minimum (σmin) principal stress values were determined. The σmax in the type 4 cortical bone was 22.56% higher than that in the type 1 bone. The σmin values in the cortical bone were similar among all the bone types. For the superstructure, increases of 9.04% in the σmax and 11.74% in the σmin in G4 (type 4 bone) compared with G1 (type 1 bone) were observed. For the implants, the highest stress values were located in G4, and the lowest values were observed in G1. In the trabecular bone, the highest stress was generated in G1 and G2. In conclusion, the more compact bones (types 1 and 2) are the most suitable for supporting full-arch implant-supported fixed prostheses, and poor bone quality may increase the risk of biological and mechanical failure.

Influence of abutment type and esthetic veneering on preload maintenance of abutment screw of implant-supported crowns.

PURPOSE: The effect of veneering materials on screw joint stability remains inconclusive. Thus, this study evaluated the preload maintenance of abutment screws of single crowns fabricated with different abutments and veneering materials. MATERIALS AND METHODS: Sixty crowns were divided into five groups (n = 12): UCLA abutment in gold alloy with ceramic (group GC) and resin (group GR) veneering, UCLA abutment in titanium with ceramic (group TiC) and resin (group TiR) veneering, and zirconia abutment with ceramic veneering (group ZiC). Abutment screws made of gold were used with a 35 Ncm insertion torque. Detorque measurements were obtained initially and after mechanical cycling. Data were analyzed by ANOVA and Fisher's exact test at a significance level of 5%. RESULTS: For the initial detorque means (in Ncm), group TiC (21.4 ± 1.78) exhibited statistically lower torque maintenance than groups GC (23.9 ± 0.91), GR (24.1 ± 1.34), and TiR (23.2 ± 1.33) (p < 0.05, Fisher's exact test). Group ZiC (21.9 ± 2.68) exhibited significantly lower torque maintenance than groups GC, GR, and TiR (p < 0.05, Fisher's exact test). After mechanical cycling, there was a statistically significant difference between groups TiC (22.1 ± 1.86) and GR (23.8 ± 1.56); between groups ZiC (21.7 ± 2.02) and GR; and also between groups ZiC and TiR (23.6 ± 1.30) (p < 0.05, Fisher's exact test). CONCLUSIONS: Detorque reduction occurred regardless of abutment type and veneering material. More irregular surfaces in the hexagon area of the castable abutments were observed. The superiority of any veneering material concerning preload maintenance was not established.

Torque stability of different abutment screws submitted to mechanical cycling.

PURPOSE: To evaluate the torque stability of different UCLA retention screws of single implant-supported crowns submitted to mechanical cycling. MATERIALS AND METHODS: Crowns fabricated from nickel-chromium-molybdenum alloy were attached to external-hexagon implants and grouped by the different retention screws used (n = 10): Ti, titanium screws (BRUNIHT, Biomet 3i); Au, gold-palladium screws with 24-carat gold coating (Gold-Tite, Biomet 3i); TiC, titanium alloy (Ti-6Al-4V) screw with diamondlike carbon coating (Neotorque, Neodent); and TiN, Ti-6Al-4V screw with aluminum-titanium-nitride coating (Ti-Tite, Conexão). Three initial removal torque (RT) values were obtained for each screw after torque insertion using an analog torque gauge. The final RT was measured after mechanical cycling (1 × 106 cycles at 2 Hz under 130 N). Data were submitted to analysis of variance and the Fischer test. RESULTS: Statistically significant differences were observed between the initial RT in groups Ti and TiN, and between TiC and TiN. No statistically significant difference was seen between mean RT obtained before and after mechanical cycling, except for the Ti screws. All groups exhibited similar torque maintenance after mechanical cycling. CONCLUSION: Although no significant difference was observed among groups for the final percentage of torque maintenance, the final RT values of the coated screws were higher than those of the noncoated screws.

The role of implant/abutment system on torque maintenance of retention screws and vertical misfit of implant-supported crowns before and after mechanical cycling.

PURPOSE: This study aimed to evaluate the role of the implant/abutment system on torque maintenance of titanium retention screws and the vertical misfit of screw-retained implant-supported crowns before and after mechanical cycling. MATERIALS AND METHODS: Three groups were studied: morse taper implants with conical abutments (MTC group), external-hexagon implants with conical abutments (EHC group), and external-hexagon implants with UCLA abutments (EHU group). Metallic crowns casted in cobalt-chromium alloy were used (n = 10). Retention screws received insertion torque and, after 3 minutes, initial detorque was measured. Crowns were retightened and submitted to cyclic loading testing under oblique loading (30 degrees) of 130 ± 10 N at 2 Hz of frequency, totaling 1 × 106 cycles. After cycling, final detorque was measured. Vertical misfit was measured using a stereomicroscope. Data were analyzed by analysis of variance, Tukey test, and Pearson correlation test (P < .05). RESULTS: All detorque values were lower than the insertion torque both before and after mechanical cycling. No statistically significant difference was observed among groups before mechanical cycling. After mechanical cycling, a statistically significantly lower loss of detorque was verified in the MTC group in comparison to the EHC group. Significantly lower vertical misfit values were noted after mechanical cycling but there was no difference among groups. There was no significant correlation between detorque values and vertical misfit. CONCLUSIONS: All groups presented a significant decrease of torque before and after mechanical cycling. The morse taper connection promoted the highest torque maintenance. Mechanical cycling reduced the vertical misfit of all groups, although no significant correlation between vertical misfit and torque loss was found.

Titanium in dentistry: historical development, state of the art and future perspectives.

Titanium is a metallic element known by several attractive characteristics, such as biocompatibility, excellent corrosion resistance and high mechanical resistance. It is widely used in Dentistry, with high success rates, providing a favorable biological response when in contact with live tissues. Therefore, the objective of this study was to describe the different uses of titanium in Dentistry, reviewing its historical development and discoursing about its state of art and future perspective of its utilization. A search in the MEDLINE/PubMed database was performed using the terms 'titanium', 'dentistry' and 'implants'. The title and abstract of articles were read, and after this first screening 20 articles were selected and their full-texts were downloaded. Additional text books and manual search of reference lists within selected articles were included. Correlated literature showed that titanium is the most used metal in Implantology for manufacturing osseointegrated implants and their systems, with a totally consolidated utilization. Moreover, titanium can be also employed in prosthodontics to obtain frameworks. However, problems related to its machining, casting, welding and ceramic application for dental prosthesis are still limiting its use. In Endodontics, titanium has been used in association to nickel for manufacturing rotatory instruments, providing a higher resistance to deformation. However, although the different possibilities of using titanium in modern Dentistry, its use for prostheses frameworks still needs technological improvements in order to surpass its limitations.

Evaluation of torque maintenance of abutment and cylinder screws with Morse taper implants.

The screw loosening of implant-supported prostheses is a common mechanical failure and is related to several factors as insertion torque and preload. The aim of this study was to evaluate the torque maintenance of retention screws of tapered abutments and cylinders of Morse taper implants submitted to retightening and detorque measurements. Two groups were obtained (n = 12): group I-tapered abutment connected to the implant with titanium retention screw and group II-cylinder with metallic base connected to tapered abutment with titanium retention screw. The detorque values were measured by an analogic torque gauge after 3 minutes of torque insertion. The detorque was measured 10 times for each retention screw of groups I and II, totalizing 120 detorque measurements in each group. Data were submitted to ANOVA and Fisher exact test (P < 0.05). Both groups presented reduced detorque value (P < 0.05) in comparison to the insertion torque in all measurement periods. There was a statistically significant difference (P < 0.05) between the detorque values of the first measurement and the other measurement periods for the abutment screw. However, there was no statistically significant difference (P > 0.05) for the detorque values of all measurement periods for the cylinder screw. In conclusion, the abutment and cylinder screws exhibited torque loss after insertion, which indicates the need for retightening during function of the implant-supported prostheses.

Preload evaluation of different screws in external hexagon joint.

PURPOSE: This study compared the maintenance of tightening torque in different retention screw types of implant-supported crowns. MATERIALS AND METHODS: Twelve metallic crowns in UCLA abutments cast with cobalt-chromium alloy were attached to external hexagon osseointegrated implants with different retention screws: group A: titanium alloy retention screw; group B: gold alloy retention screw with gold coating; group C: titanium alloy retention screw with diamond-like carbon film coating; and group D: titanium alloy retention screw with aluminum titanium nitride coating. Three detorque measurements were obtained after torque insertion in each replica. Data were evaluated by analysis of variance (ANOVA), Tukey's test (P < 0.05), and t test (P < 0.05). RESULTS: Detorque value reduced in all groups (P < 0.05). Group A retained the highest percentage of torque in comparison with the other groups (P < 0.05). Groups B and D retained the lowest percentage of torque without statistically significant difference between them (P > 0.05). CONCLUSIONS: All screw types exhibited reduction in the detorque value. The titanium screw maintained the highest percentage of torque whereas the gold-coated screw and the titanium screw with aluminum titanium nitride coating retained the lowest percentage.

Planning for immediate loading of implant-supported prostheses: literature review.

The aim of this study was to present the factors that influence planning for immediate loading of implants through a literature review for treatment success. Research was conducted in the PubMed database including the key words immediate implant loading, implant-supported prostheses, and implant planning for studies published from 2000 to 2011. Forty-eight articles were used in this review to describe the indications and counterindications, presurgical planning, and technologies available for planning of this treatment alternative.

Esthetics in implant-supported prostheses: a literature review.

Esthetics is important for success of implant-supported prostheses. This study aimed to review esthetics concepts for implant treatment. Research in the PubMed database included studies published from 1995 to 2010 with the keywords implant esthetics, implant-supported prostheses, and esthetics. Forty-five studies were evaluated regarding the presurgical planning, surgical phase, and temporary and final restoration phases. It was concluded that esthetics in implant-supported prostheses results from a multidisciplinary approach from planning until insertion of the final restoration.

Avaliação da confiabilidade e modo de falha de coroas cerâmicas parafusadas a implantes osseointegráveis de diferentes conexões / Evaluation of reliability and failure mode of screw-retained all-ceramic crowns attached to osseointegrated implants with different connections

Introdução: A performance de restaurações cerâmicas parafusadas a implantes com diferentes conexões diante de fadiga é um fator importante para o sucesso do tratamento. Proposição: O objetivo do estudo foi avaliar a confiabilidade e o modo de falha de coroas cerâmicas obtidas com pilares de zircônia parafusadas a implantes osseointegráveis de diferentes conexões. Material e método: Foram formados 3 grupos de acordo com as diferentes conexões pilar-implante: Grupo EH - hexágono externo, Grupo IH - hexágono interno e Grupo MT - Cone Morse. As coroas foram obtidas através da aplicação de cerâmica de revestimento sobre pilar de zircônia utilizando a técnica de aplicação em camadas e parafusadas aos implantes com parafusos de retenção específicos para cada sistema. Os espécimes foram submetidos ao teste de fadiga acelerado step-stress de acordo com os perfis leve (n=9), moderado (n=6) e agressivo (n=3) determinados após teste de resistência à fratura (n=4) em máquina de ensaio universal. Os dados foram inicialmente avaliados pela análise de use level probability Weibull. Os valores e intervalos de confiabilidade foram obtidos através de standard probability calculation. Considerando os valores de carga para a falha dos espécimes, foi calculada a distribuição de Weibull. Análise fractográfica foi conduzida através de estereomicroscopia e microscopia eletrônica de varredura. Resultado: O valor de β de todos os grupos (EH-β= 0,6307; IH-β=0,9730; MT-β=0,1942) sugere que as falhas foram mais associadas ao nível de carga do que ao dano acumulado. Os valores de confiabilidade para uma missão de 50.000 ciclos e carga de 400 N foram de 97% para o grupo EH, 46% para o grupo IH e 0,5% para o grupo MT com diferença estatisticamente significante entre si. Já para uma missão de 50.000 ciclos e carga de 200 N, os valores de confiabilidade foram de 100% para o grupo EH, 98% para o grupo IH e 89% para o grupo MT. Nesse caso, não houve diferença estatisticamente significante entre...

Introduction: The performance of screw-retained all-ceramic crowns attached to implants with different connections under fatigue is a relevant factor for treatment success. Purpose: The aim of this study was to evaluate the reliability and failure mode of screw-retained all-ceramic crowns fabricated with zirconia abutments attached to osseointegrated implants with different connections. Material and method: Three groups were designed according to the implant-abutment connection: Group EH - external hexagon, Group IH - internal hexagon and Group MT - Morse taper. Layering technique was used for veneering of zirconia abutments. The crowns were attached to the implants with the retention screws of each system. Step-stress accelerated fatigue test was conducted according to mild (n=9), moderate (n=6) and aggressive (n=3) profiles determined after single-load-to-fracture test (n=4) in a universal testing machine. Data was previously analyzed by use level probability Weibull. Standard probability calculation was used to determine the reliability and confidence bounds. Weibull distribution was calculated based on the load to failure. Failure modes were described under light polarized microscopy and scanning electron microscopy. Result: β of all groups (EH-β= 0.6307; IH-β=0.9730; MT-β=0.1942) suggested that failure was associated to load instead of cumulative damage. Significant difference was observed between the groups for the calculated reliability in a mission of 50,000 cycles at 400 N (97% for group EH, 46% for group IH and 0.5% for group MT). For a mission of 50,000 cycles at 200 N, the calculated reliability was 100% for group EH, 98% for group IH and 89% for group MT. There was no significant difference between EH and IH and between IH and MT. Weibull distribution revealed descending β and η for the groups EH (β=13.05/η=561.81), IH (β=5.81/η=513.45) and MT (β=5.31/η=333.23) and significant difference between the groups. Group EH showed veneer cohesive failure...

Avaliação da confiabilidade e modo de falha de coroas cerâmicas parafusadas a implantes osseointegráveis de diferentes conexões / Evaluation of reliability and failure mode of screw-retained all-ceramic crowns attached to osseointegrated implants with different connections

Introdução: A performance de restaurações cerâmicas parafusadas a implantes com diferentes conexões diante de fadiga é um fator importante para o sucesso do tratamento. Proposição: O objetivo do estudo foi avaliar a confiabilidade e o modo de falha de coroas cerâmicas obtidas com pilares de zircônia parafusadas a implantes osseointegráveis de diferentes conexões. Material e método: Foram formados 3 grupos de acordo com as diferentes conexões pilar-implante: Grupo EH - hexágono externo, Grupo IH - hexágono interno e Grupo MT - Cone Morse. As coroas foram obtidas através da aplicação de cerâmica de revestimento sobre pilar de zircônia utilizando a técnica de aplicação em camadas e parafusadas aos implantes com parafusos de retenção específicos para cada sistema. Os espécimes foram submetidos ao teste de fadiga acelerado step-stress de acordo com os perfis leve (n=9), moderado (n=6) e agressivo (n=3) determinados após teste de resistência à fratura (n=4) em máquina de ensaio universal. Os dados foram inicialmente avaliados pela análise de use level probability Weibull. Os valores e intervalos de confiabilidade foram obtidos através de standard probability calculation. Considerando os valores de carga para a falha dos espécimes, foi calculada a distribuição de Weibull. Análise fractográfica foi conduzida através de estereomicroscopia e microscopia eletrônica de varredura. Resultado: O valor de β de todos os grupos (EH-β= 0,6307; IH-β=0,9730; MT-β=0,1942) sugere que as falhas foram mais associadas ao nível de carga do que ao dano acumulado. Os valores de confiabilidade para uma missão de 50.000 ciclos e carga de 400 N foram de 97% para o grupo EH, 46% para o grupo IH e 0,5% para o grupo MT com diferença estatisticamente significante entre si. Já para uma missão de 50.000 ciclos e carga de 200 N, os valores de confiabilidade foram de 100% para o grupo EH, 98% para o grupo IH e 89% para o grupo MT. Nesse caso, não houve diferença estatisticamente significante entre...

Introduction: The performance of screw-retained all-ceramic crowns attached to implants with different connections under fatigue is a relevant factor for treatment success. Purpose: The aim of this study was to evaluate the reliability and failure mode of screw-retained all-ceramic crowns fabricated with zirconia abutments attached to osseointegrated implants with different connections. Material and method: Three groups were designed according to the implant-abutment connection: Group EH - external hexagon, Group IH - internal hexagon and Group MT - Morse taper. Layering technique was used for veneering of zirconia abutments. The crowns were attached to the implants with the retention screws of each system. Step-stress accelerated fatigue test was conducted according to mild (n=9), moderate (n=6) and aggressive (n=3) profiles determined after single-load-to-fracture test (n=4) in a universal testing machine. Data was previously analyzed by use level probability Weibull. Standard probability calculation was used to determine the reliability and confidence bounds. Weibull distribution was calculated based on the load to failure. Failure modes were described under light polarized microscopy and scanning electron microscopy. Result: β of all groups (EH-β= 0.6307; IH-β=0.9730; MT-β=0.1942) suggested that failure was associated to load instead of cumulative damage. Significant difference was observed between the groups for the calculated reliability in a mission of 50,000 cycles at 400 N (97% for group EH, 46% for group IH and 0.5% for group MT). For a mission of 50,000 cycles at 200 N, the calculated reliability was 100% for group EH, 98% for group IH and 89% for group MT. There was no significant difference between EH and IH and between IH and MT. Weibull distribution revealed descending β and η for the groups EH (β=13.05/η=561.81), IH (β=5.81/η=513.45) and MT (β=5.31/η=333.23) and significant difference between the groups. Group EH showed veneer cohesive failure...

The effect of mechanical cycling and different misfit levels on Vicker's microhardness of retention screws for single implant-supported prostheses.

PURPOSE: The aim of this study was to evaluate the effect of mechanical cycling and different misfit levels on Vicker's microhardness of retention screws for single implant-supported prostheses. MATERIALS AND METHODS: Premachined UCLA abutments were cast with cobalt-chromium alloy to obtain 48 crowns divided into four groups (n = 12). The crowns presented no misfit in group A (control group) and unilateral misfits of 50 µm, 100 µm, and 200 µm in groups B, C, and D, respectively. The crowns were screwed to external hexagon implants with titanium retention screws (torque of 30 N/cm), and the sets were submitted to three different periods of mechanical cycling: 2×10(4) , 5×10(4) , and 1×10(6) cycles. Screw microhardness values were measured before and after each cycling period. Data were evaluated by two-way ANOVA and Tukey's test (p < 0.05). RESULTS: Mechanical cycling statistically reduced microhardness values of retention screws regardless of cycling periods and groups. In groups A, B, and C, initial microhardness values were statistically different from final microhardness values (p < 0.05). There was no statistically significant difference for initial screw microhardness values (p > 0.05) among the groups; however, when the groups were compared after mechanical cycling, a statistically significant difference was observed between groups B and D (p < 0.05). CONCLUSIONS: Mechanical cycling reduced the Vicker's microhardness values of the retention screws of all groups. The crowns with the highest misfit level presented the highest Vicker's microhardness values.